Vaibhavrocky :
I want to upgrade my ASUS k53sm ram to 8gb. It has an Elpida stick of 4gb and 11 CAS latency. Which RAM should I purchase, a 1.35v or 1.5v. Also tell me the CAS latency to select and whether to buy a new 8 gb stick or add another 4gb stick beside the elpida?
Asus K53SM Laptop supports 2 x 4 GB Max. Laptops that support the 1.5v memory will support 1.35v as well, but if you mix two different voltages, it will run in 1.5v. The existing Elpida memory will be 1.5v and the standard memory that comes with the Asus K53SM is 1333 MHz. You can mix different speeds as well. But better to go with same speed.
Single 8 GB RAM is not supported.
Refer this link for compatible Asus K53SM Laptop RAM upgrade:
http://www.memorystock.com/memory/ASUSK53SM.html